Effect of Specimen Geometry on Hot Torsion Test Results for Solid and Tubular Specimens

Hot torsion tests have been carried out on aluminum, stainless steel, and silicon steel specimens using a wide range of gage length: radius ratios and bore diameters. For stainless steel, which dynamically recrystallises, a higher strain to maximum stress was found for specimens with a gage length : radius ratio <2. Other stress-strain data were unaffected. The use of tubular specimens did not alter deformation curves at low strains but ductility was reduced for large bore sizes, apparently because average rates of crack propagation through the wall were increased. A new effective radius is proposed for calculation of strains, strain rates, and shear stresses from torque-twist data for solid and tubular specimens.